An air conditioner using a heat pump system has a heating operation mode and a cooling operation mode as the basic operation modes, and at the time of the cooling operation mode and a dehumidifying operation mode (dry operation mode), condensed water adheres to an indoor heat exchanger included in a refrigerating cycle.
Usually, the condensed water is discharged to the outside of a room through a drain pan, but it is not always discharged completely, and sometimes remains in the drain pan after the stoppage of operation.
In this case, dust etc. adhere to the remaining condensed water, by which fungus and other various bacteria develop and propagate, and thereby emitting unpleasant smell. Also, the humidity in the indoor unit is raised by the remaining condensed water, which also emits extraordinarily unpleasant smell.
In such a situation, there has been proposed an air conditioner which performs interior drying operation for drying the interior of indoor unit to prevent the development of various bacteria and the emission of unpleasant smell caused by the remaining condensed water (for example, see Japanese Patent Application Publications No. 9-126528 and No. 10-62000).
The invention described in the Application Publication No. 9-126528 is configured so that when the operation of air conditioner is stopped, air blowing operation or heating operation is performed for a certain period of time (for example, three minutes) to dry the interior of indoor unit, and especially after cooling operation or dehumidifying operation, the interior of indoor unit is dried by prolonging that period of time.
Also, the invention described in the Application Publication No. 10-62000 is configured so that heating operation of air conditioner is started when it is detected that cooling operation has been finished, and during the heating operation, a compressor and an indoor fan are rotated at a low speed, and the operation thereof is performed for a fixed period of time (for example, three minutes).
However, in the aforementioned invention described in the Application Publication No. 9-126528, since the interior of indoor unit is dried mainly by air blowing operation using the indoor fan only, it inevitably takes time to sufficiently dry the interior of indoor unit. For example in a situation of high humidity, it is difficult to sufficiently dry the interior of indoor unit by drying operation for a period of time as short as three minutes.
Also, since the internal situation of indoor unit differs depending on the operation time of cooling operation or dehumidifying operation, even if heating operation is additionally performed, when the heating operation time is fixed, the operation time for drying the interior of indoor unit becomes longer than necessary, or contrarily the operation for drying the interior of indoor unit becomes insufficient, which poses a problem in that proper drying operation is not performed.
In particular, the drying operation performed longer than necessary is unfavorable from the viewpoint of energy saving, and contrarily the insufficient drying operation leads to the development of various bacteria and the emission of unpleasant smell.
In the aforementioned invention described in the Application Publication No. 10-62000, since heating operation is started immediately after cooling operation, humidified air with a relative humidity of approximately 100% is blown from the indoor unit, which sometimes gives unwell feeling to the user. Also, the humidified air may produce dew condensation in the indoor unit. Moreover, since the heating operation time is fixed, there arises the same problem as that with the invention described in the Application Publication No. 9-126528.